Method of making seamless tubing.



No. 870,246. PATENTED NOV. 5, 1907.

J. H. NICHOLSON.

METHOD OF MAKING SEAMLESS TUBING.

APPLICATION FILED 930.15, 1904.

WITNESSES INVENTOR wmmcwu 7 JV. MAW :2 Wm

UNITED STATES PATENT OFFICE.

JOHN H. NICHOLSON, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO NATIONAL TUBE COM- PANY, OF PITTSBURG, PENNSYLVANIA, A CORPORATION OF NEW JERSEY METHOD OF MAKING SEAMLESS TUBING.

Specification of Letters Patent.

Patented Nov. 5, 1907.

Application filed December 15. 1904- Serial No. 237,012.

drawings, forming part of this specification, in which' the figure is a plan view of apparatus arranged to carry out my'invention.

Heretofo're in the manufacture of hot-rolled blanks frompierced billets for the purpose of cold drawing, a plug mill of the well-known type is one of the common 'devices that has been used; the hollow billet is elongated in this mill and the thickness of its wall reduced to a sufficient gage or thinness, so that the same can be cold-drawn with smooth surfaces to the desired thickness of wall. In this plug mill operation it is desirable to produce hot-rolled blanks, or tubes, as round and as smooth on the inside as possible, to facilitate the colddrawing and enable the tube. to be finished to the desired gage and to smooth-finish it in as few cold-drawing passes as possible. Heavy reductions cannot be taken on the cold draw bench, without excessive breakage, until the rolled blank has been rounded up and the inten'or scratches removed, owing to the tendency of the metal-to pick up, or accumulate, ahead of the mandrel during the cold-drawing. To partly overcome this difficulty, the rolled blanks are. given several addi'-.

tional passes on the plug-mill for the purpose of rounding up the diameter and smoothing vthe interior surface, little or no work being done in reducing the thickness of well during such additional passes. This additional work for the plug-mill occupies much time, and reduces the output of the mill.

My invention is designed to overcome this difiiculty, so that the plug-mill may be used for its normalfunction of reducing the thickness and elongating the blank, without giving further passes on such mill for rounding up and working out the scratches, thereby reducing the number of passes that have been heretofore deemed necessary in the production of hot-rolled blanks, suitable for colddrawing. For this purpose I subject the blank to a new operation, intermediate between the plug-mill and the draw-bench. In this additional step I pass the rolled blank through a reeling, or cross-rolling machine, in which the blank is rounded up, its intenor and exterior surfaces smoothed, and the scratches practically eliminated, giving a much better blank or tube for cold-drawing than could be produced on the plug-mill, no matter how many additional passes for rounding and smoothingwere given. I

In addition to increasing the output of the plug-mill by using this new and intermediate operation, it reduces the number of passes heretofore required on the cold draw bench, as the reeled. tube is round and smooth, and a heavy draft, or pull, can be taken in the first pass over the bench, without fear of excessive breakage. This is not possible under the old method of operating, as the first pass over the bench is mainly used to round up the billet and smooth out the interior scratches.

In thedrawings, in which I show one form of apparatus for carryingout my invention, 2 indicates a plugmill which'is preferably of the type shown in the patent to myself and R. C. Stiefel'No. 770,195, dated September, 13th, 1904, having a driving connection 3 arranged to drive apair of rolls continuously in the samedirection.- The upper roll is vertically movable in its housing to provide for separating the rolls sufficiently forthe return feeding of the tube. The means for moving the upper rolls may be of any desirable type, such for example as shown in our patent above referred to. On the feedingside of the rolls is a feed-trough 4 mounted on supports movable on transverse tracks 5 to bring the table into line with any ofthe roll passes.

On the delivery side of the rolls are rods 6 which are fixed'at the rear end and extend through suitable supports to the respective roll passes, being formed at their ends to receive the mandrel'plugs over which the tubes are rolled. The tubes are stripped from the rods and returned to the feeding side in the same axial line as m that of the delivery, by suitable mechanism, such as shown in our patent, the blank being thus fed forwardly into the bite of the rolls and rolled over one. of the plugs and rods. The mandrel plug is then removed, the rolls are moved apart, and the blank is stripped backwardly over the mandrel rod in the same line, moving backwardly through the pass. The mandrel plug is then replaced, the rolls are brought more closely together than in the previous rolling, and the operation is repeated. The plug rolling may be completed in the same pass, or in successive passes.

The plug-mill shown and described is not essential to my invention as the pierced billets may be taken di-' rectly to the reeling mill in making heavy gages. Any desirable type of plug-mill may be used, though I prefer the one shown, since its operation is so rapid that the blank may be reduced suflicientlyfor drawing, before the metal has become too cold. I i -A fter the plug-mill rolling ,fs completed the tube is returned to the feeding side. and rolls down over inclined skidways 7 upon feeding rollers 8. These rollers may be driven by bevel-gear connection with the shaft 9, driven from the motor 10. This roller table feeds the hot tube forwardly to the reeling mill 11. This reeling mill is preferably provided with a pair of positively driven skewrollers 12 by which the tube is rolled over a mandrel 13, the head of which is preferably straight and of the same diameter throughout.

In this operation the tube is cross-rolled over the mandrel, thus practically eliminating scratches or internal grooves and giving it. a smooth inner siuface. At the same time the tube is straightened, though the essential function of the reelingmill is to eliminate the internal scratches and give an inner surface smooth enough for rapid and eflicieut drawing. After this cross-rolling the mandrel rod is drawn out of the tube by stripping mechanism indicated at 14, and rolls out sidewise over skids 15. The tube is then ready for the cold-drawing operation.

The advantage of increased output of the plug-mill, and decreased number of cold-drawing passes, will be appreciated by those skilled in the art, and results in a decided material decrease in the cost of production.

As is well known to those skilled in the art of making seamless tubes, in reducing the thickness of wall of a pierced billet by drawing through a groove and overa plug the friction is very great, and it is impossible to prevent the plug from grooving and scoring the interior wall of the tube, resulting in the formation of ridges and grooves therein which cannot be removed, no matter how many additional passes are given over the plug. If the ridged or grooved tube is of approXimately the right sizoand thickness of wall, and an additional pass is used to smooth up the inside, the wall of the tube is made too thin, If however, such a tube is cross rolled, or reeled, in the manner herein before described, the metal at the ridges is displaced and flows into the hollows, or grooves, without reducing the thickness of the wall, the gage is trued up, and there results a tube having a smooth surface, both interiorly and exteriorly. In fact, the described method of cross-rolling, or reeling the tube has proven so satisfactory that cold drawing is, in some cases, rendered unnecessary. It also results in a material saving in dies and mandrels, owing to the fact that only round, smooth tubes are drawn. Heretofore the breaking-down pass has been very severe on these tools, and I have found that by the use of reeled tubes the expense for tools has been materially reduced. The reeling operation presents the same advantages in treating pierced billets without plug rolling, since such billets are rough and grooved on their interior.

The reeling mill may be of any desirable type so long as it performs the function of smoothing out the scores or grooves on the interior of the tube. The other parts of the apparatus may be varied widely without departing from my invention.

I claim 1. The herein described improvement in the manufacture of seumlesstubing, which consists in cros s-rolling the tube over a mandrel to remove interior scores or grooves and to true up its gage, without materially reducing the thickness of its wall; substantially asdescribed.

2. The herein described method of making seamless tubing which consists in rolling the p ierced blank or billet in a plug-mill, then removing the blank and cross rolling it over a mandrel to eliminate interior ridges or grooves and to true up the gage: substantially as described.

3. The herein described method of making seamless tubing which consists in rolling the pierced billet or blank in a plug-mill, then removing the blank and cross-rolling it over a mandrel to smooth out the interior grooves and ridges, and to true up the gage, without materially reducing the thickness of wall, and subsequently colddrawing the tube; substantially as described.

-t. In the method of making seamless tubing, the steps which consist in elongating and thinning the-pierced billet in :1 plug-mill, and then removing the blank and crossrolling it over a mandrel to smooth out the interior scores or grooves while the blank is hot, Without materially changing the thickness of. its wall; substantially as described.

5. In the method of making seamless tubing, the following steps: elongating and thinning the pierced billet by rolling it over a plug, then removing the hot blank and rolling it over a mandrel to smooth out its interior Withnut changing its gage, and then cold-drawing the blank,

substantially as described.

In testimony whereof, I have hereunto set my hand.

JOHN H. NICHOLSON.

Witnesses JOHN MILLER, H. M. Conwm. 

